This invention relates to an accessory to be used with an optical instrument and, more particularly, to an appliance designed to convert a reflectance measuring instrument to a transmittance measuring instrument.
Optical instruments measuring color and also analyzing the constituents of a sample are typically designed to make measurements by the reflectance of light energy from the sample. In the case of some samples, it is desirable to use the same instruments to measure the transmittance through a sample. Prior to the present invention, appliances had been employed to convert reflectance measuring instruments into transmittance measuring instruments by housing a lamp in the appliance, which then directed a beam of light through a sample into the reflectance measuring instrument. The instrument analyzed the light transmitted through the sample with the same hardware employed to analyze reflected light from the sample. Because the lamp in the appliance generated heat, a fan was necessary also in the appliance to keep the appliance cool. However, even with the fan, the appliance tended to overheat. To supply power to the lamp and to the fan, a plug, a connecting cable and a power switch were required. In order to allow field installation of the accessory, the connecting hardware had to be built into every instrument whether or not the instrument employed the appliance. A major problem with the appliance was that the internal lamp in the base instrument used to make reflectance measurements ahd to be turned off so that light from this lamp could not interfere with the transmittance measurement. When the lamp in the base instrument was turned back on, further measurements had to be delayed to allow the instrument to warm up again before reflectance measurements could be made. Also, when the lamp in the appliance was turned on to perform a transmittance measurement, the appliance had to be allowed to warm up before it could be used.